Several models have been developed in the applicant's laboratory for the eradication of advanced syngeneic antigenic murine leukemias and sarcomas by a combination of non-curative chemotherapy and adoptively transferred lymphoid cells. The objective of the proposed research is to further study the prerequisites for efficacy of such "adoptive chemoimmunotherapy" with syngeneic and allogeneic lymphoid cells and explore some of the problems posed by those prerequisites so as to lend rational direction to eventual attempts at a similar immunotherapy in man. The principal problems to be investigated will be the following: 1) the antitumor reactivity of mice bearing leukemia and the infuence of therapy on such reactivity, 2) the sensitization of lymphoid cells to tumor antigens in vitro and their immunotherapeutic efficacy in vivo, 3) the therapeutic use of lymphoid cells "armed" in vitro with specific antiserum, 4) prevention and treatment of graft versus host disease (GVHD) by "hot pulse suicide" techniques in vitro and immunosuppressive agents in vivo, and 5) the use of GVHD preferentially or specifically against the leukemia. The availability in the same laboratory of effective and reproducible models for adoptive chemoimmunotherapy and for induction of fatal GVHD in vivo and assays for cell mediated immunity to tumor and non-tumor antigens in vitro will hopefully make it possible to attain those objectives.